In the latest tests, Si and colleagues at Rice, China's Zhejiang University, UCLA, Los Alamos National Laboratory and the State University of New York at Buffalo (SUNY-Buffalo) sought to move the system in the other direction, toward Mott localization.
"We wanted to decrease the kinetic energy by expanding the distance between iron atoms in the lattice," said study co-author Jian-Xin Zhu, a theorist from Los Alamos. "Unfortunately, there is no pnictide material with those properties."
So the team's experimentalists, Rice's Emilia Morosan and Zhejiang's Minghu Fang, hit upon the idea of substituting a similarly patterned material called an iron oxychalcogenide (pronounced: OXY-cal-cah-ge-nyde). Like the iron pnictides, iron oxychalcogenides are layered materials. But compared with the pnictides, the distance between iron atoms is expanded in the oxychalcogenides.
Tests on the new materials confirmed the theoretical predictions of the team; a slight expansion of the iron lattice pushed the system into a Mott insulating state.
"Our results provide further evidence that the undoped iron pnictide parent compounds are on the verge of Mott localization," Abrahams said.
|Contact: Jade Boyd|